Optical cutting edge locators for cutting apparatus are known and increase the accuracy and efficiency of the cutting operation. U.S. Pat. No. 4,503,740 discloses one example of such an apparatus, wherein an optical beam is directed toward a workpiece to assist the operator to align the workpiece with the cutting device prior to being cut.
Other devices are known in which lasers are used to assist the operator in pre-positioning letters, characters, or other objects on the work surface. U.S. Pat. No. 7,219,437 discloses one example of such a device.
Other examples in which optical markers are employed to assist the operator in marking the workpiece prior to cutting or prior to positioning objects and the like are disclosed in U.S. Pat. Nos. 7,469,480 and 7,484,304 and U.S. Patent Publication No. 2010/0257985.
In the aforementioned examples, the optical marking is employed prior to either cutting the workpiece or positioning or affixing the object to a desired location on the workpiece.
In the papermaking industry, a papermaking furnish is applied from a headbox onto a moving wire of a fourdrinier machine, to form a fiber web. So-called “trim squirts” are used to eject high-pressure, focused, water jets toward the fiber web, which cut the fiber web leaving a smooth edge. The thus-cut trim sections are separated from the fiber web, and the remaining fiber web undergoes further processing into a paper product. Operators can adjust the water jet equipment, for example, to modify the width of the fiber web. It is very difficult, however, to accurately cut the fiber web with the trim squirts such that the width of the fiber web and its position relative to the cross direction of the wire are accurately known. The trim squirts may get knocked out of line or be subject to changes or degradation in the nozzle, water pressure, and the like, which affects the cut location relative to the nozzle position. Efforts have been made to improve the trim squirts, such as making them adjustable, more operationally durable, etc., but despite these efforts, the present inventors have found that it is difficult to reliably coordinate the cut location in the fiber web with the position of the trim squirt nozzle. Heretofore, to compensate for the variability in the trim squirt position, operators typically held a standard tape measure over the moving web to measure the distance between a fixed reference on the machine and the trim cut or cut line. In practice, and under typical operating conditions, this method of measuring results in an estimate of the measurement and is dependent on the individual judgment of the particular operator taking the reading. This method is satisfactory on conventional papermaking machines using conventional headbox technology, e.g., air-padded headboxes.
As paper machines around the world upgrade to hydraulic headbox technology, the ability to reduce the product's weight variability in the cross direction of the papermaking machine has increased as a result of increasing the amount of dilution actuators across the machine. In the hydraulic headbox, dilution actuators are mapped to corresponding positions on the corresponding product weight scanner.
The inventors have found that as the number of weight measurement zones in the product weight scanner increases, the need for precise trim squirt positions (given by trim measurements) used in the dilution actuator to corresponding weight mapping and other mapping has become a critical-to-operate measurement. The inventors have found that conventional methods of locating and measuring trim cut positions are unsatisfactory and unsuited for use with new papermaking technologies, such as the new hydraulic headboxes, weight-zone mapping, and the like.